The protozoan parasite E. histolytica, the causative agent of amebic dysentery and amebic liver abscess, remains a major cause of morbidity and mortality worldwide. Despite the medical importance of this pathogen, much remains to be learned about the role of the immune system in resistance to E., histolytica infection. While cell mediated immunity is felt to be involved in protection against invasive amebiasis, studies of human cellular immune responses to amebae have been limited. One of the problems with previous studies was the inability to study chemically defined amebic antigens. This FIRCA proposal describes a collaborative effort between the laboratory of Dr. Jesus Calderon, and Dr. Samuel L. Stanley, Jr., to analyze cellular immune responses to a panel of defined recombinant amebic antigens. Peripheral blood mononuclear cells (PBMC) from patients with amebic liver abscess, intestinal amebiasis, previous amebic infection, and healthy controls will be examined for proliferative responses to recombinant E. histolytica antigens, and to synthetic peptides derived from the serine rich E. histolytica protein (SREHP), a major surface antigen of amebae. These studies may provide insights into immune mechanisms underlying susceptibility to invasive amebic disease, and will provide important information on the T-cell immunogenicity of SREHP, a candidate vaccine molecule.